kapil,

as erik said, a design with a 8255 is troublesome. I used that thing in middle 80s with Z80 CPUs.

but if you really want to try a 8255, look at some designs like that from paulmon as example:

http://www.pjrc.com/tech/8051...matic.html

that were tested and tried (and even the author acknowledges that it's difficult to troubleshoot...)

It's a circuit with latches and address decoders. I think that you are doing something like this.

hth

orlando